Duplex radio aerial system



Dec. 15, 1936.

J. G. ACEVES DUPLEX RADIO AERIAL SYSTEM Filed July 25, 1955 2Sheets-Sheet 1 at Mi Julius aflceves BY M, m+w

NEYS

Dec. 15, 1936. J. G. ACEVES DUPLEX RADIO AERIAL SYSTEM Filed July 25,1935 2 Sheets-Sheet 2 INVENTOR Julius fiiAcel as ORNEYS Patented Dec.15, 1936 UNITED STATES PATENT OFFICE DUPLEX RADIO AERIAL SYSTEMApplication July 25; 1935, Serial No. 33,099

8 Claims. (Cl. 250-33) This invention relates to radio antenna systemsand associated down lead circuits for electrically coupling the antennato a radio receiver.

. More particularly the invention pertains to systems of this charactersuitable for so-called "all wave radio reception including the presentUnited States and European broadcast bands, as

well as the short wave range covering a total frequency band of about.15 to 23 megacycles. 10 An object-of the invention is to provide acombined antenna and down lead system which will afiord efiicient radioreception within extremely wide frequency limitssuch as thosementionedwithout necessity for switching operations in passing from oneWave band to the other. Further objects are to so arrange the down leadcircuit and associated terminating couplings as to prevent interferencepicked up from such local equipment as sparking motors, electricalrefrigerators, neon signs, etc., by the down lead conductors and groundconnections from entering the radio receiver.

In Patent No. 1,965,539 issued jointly to E. V. Amy and myself, antennaand down lead systems generic to the present invention, are describedtogether with specific embodiments thereof wherein electrostaticcouplings designed for eflicient short wave reception are providedbetween the antenna and down lead circuits, and wherein eflicientreception at the longer wave lengths is secured by means ofelectromagnetic or transformer couplings. In the systems of the patent,local interference picked upby the down leads is prevented from enteringthe receiver by tapping the midpoint of the antenna transformer 8secondary winding through its primary winding to the antenna, and byfurther terminating the down lead circuit adjacent the receiver in acoil centrally tapped to ground.

The present invention provides systems basically like those of thepatent but difiering specifically therefrom in the provision between theantenna and down leads of electromagnetic or transformer couplingsdesigned for short as well as for long wave reception; and in theutilization of novel couplings between the down leads and the radioreceiver employing coils and condensers so arranged and proportioned asto relay signals eificiently at both long and short waves, while incooperation with the antenna couplings preventing interference picked upby the down leads and ground connections from entering the receiver.

In the drawings:

Fig. 1 shows in the form of a circuit diagram lead circuit to thereceiver; while 7 10 Fig. 4 shows a modification of the Fig. 1 cir- Quitadapted to prevent interference picked up by the ground lead as well asby the down leads from entering the receiver.

The system of Fig. 1 comprises a dipole type 15 of antenna A, A1inductively coupled, in a manner to be explained, through short and longwave transformers T1 and T2 to down leads L1, L2, preferably of twistedpair, extending to a set coupler comprising short and long wavetransformers Ta'and Ti, having primary windings P3 and Pi respectively,effectively connected in parallel between the down leads L1, L2, andsecondary windings S3, Si effectively connected in parallel to the inputto a radio receiver of the all wave type indicated schematically at R. v25 Short wave reception is based on a difierence of potential producedby the received signals between the portions A, A1 of the aerial wherebya current is will be caused to flow in the primary winding P1 oftransformer T1 centrally disposed in the aerial. The resulting voltageinduced in the associated secondary windings S1 having their outerterminals connected to the down leads L1, L2 respectively and theirinner terminals connected through a short wave by-pass condenser C1.will cause a circulating circuit ie to flow in the down lead circuitcomprising: the secondary windings S1 and condenser C1, referred to,down leads L1, L2 and the primary circuit of the set couplertransformers T. and T4.

The antenna is preferably of such length that it functions substantiallyas a doublet antenna at short wave lengths. For short wave reception alength of approximately 20 meters for the antenna will operateelfectively.

The circulating circuit is produced in the manner explained and flowingover the down leads L1, L2, will cause the short wave signals to beselectively relayed through the short wave transformer T3 to thereceiver R. This automatic selection results in part from providingrelatively low inductance windings on the short wave transfomer T3 andrelatively high inductance windings on the long wave transformer T4, and

in part from the insertion of condensers Ca, Ca, and C4 in seriesrespectively with the primary and secondary windings of transformer T3.The capacities of these condensers are such that they offer smallimpedance to short waves whereas they substantially block the longwaves. Accordingly at short wave lengths the short wave transformer '1':presents a lower impedance between down leads L1, L2 than does the longwave transformer which acts substantially as a choke. Conversely at longwave lengths the long wave length transformer T4 presents a. lowerimpedance path owing to the blocking action of the condensers Ca, C3, C4in series with the short wave transformer windings. Thus the short wavesignals will pass more easily through transformer Ta and the long wavesignals more easily through transformer T4. 1

At long waves the antenna A, A1 in conjunction with the down leads L1,L2 operates as a horizontal T antenna. Long wave reception in accordancewith the invention is based on the establishment by the received signalsof a difference of potential between theantenna and, either ground or acounterpoise. For this reason the long'wave antenna transformer must beso arranged as to permit signaling current to flow between the antennaand ground and to convert this current into a circulating current ie inthe down lead circuit. This is accomplished by connecting the secondarywinding S1 of the long wave transformer T: in shunt to condenser C1 atthe midpoint of the short wave transformer secondary S1; by furtherconnecting the primary winding P2 of the long wave transformer T2 in aconnection M extending from the midpoint of its secondary winding S2 tothe midpoint of the short wave transformer primary winding P1 in serieswith the antenna;' and finally by connecting the midpoints of the setcoupler transformer primaries Pa and P4 to ground at G as shown.

The capacity of condenser C1 is such that although at short wave lengthsit functions as a by-pass condenser as stated, at long wave lengths itacts as a blocking condenser, thereby in conjunction with transformersT1 and T2 providing eflicient transfer of signaling energy between theantenna and the down lead circuit at both short and long wave lengths.

With the circuit as shown in Fig. l, the long wave signals picked up bythe antenna will produce currents i1. flowing simultaneously from theportions A, A1 of theantenna and in inductive opposition through thehalves of coil P1 to its midpoint, thence over the midtap connection Mthrough the primary P: of the long wave transformer to the midtap on thesecondary S2, where the current divides and flows in equal amounts asparallel currents through the down leads L1,- La, and thence ininductive opposition throughthe halves of the primary windings P3. P4 oftransformers T3, T4 to ground at G of the receiver R.

These parallel currents will of themselves produce substantially nosignal voltage in the secondary windings S1, S4 of transformers T3, T4,since these currents flow, as stated, in inductive opposition in thehalves of .the primary windings P3, P4 and hence induce no secondaryvoltages. However, the total current i1., in traversing the primarywinding P: of the long wave antenna transformer, induces a voltage inthe associated secondary S: which establishes a circulating current isin the down lead circuit, which current traverses in the same directionthe entire primary winding P4 of the long wave -set coupler transformerT4, and thereby induces a signal voltage in the associated secondary S4which actuates the receiver R.

Consider now the effect of electrical interference, such as that causedby a sparking motor of an electric refrigerator, etc., picked. up by thedown leads L1, L2, as indicated by e1. Waves e1 will establish in therespective down leads L1,

L2, currents i1, i: of the same instantaneous magnitude and poled in thesame direction.

These parallel currents in passing to ground at G, will likewisetraverse the halves of the set coupler primary transformer windings P3,P4, in inductive opposition with the result that no voltage will beinduced in the associated secondaries, as has been explained. In thisway interference picked up by the down leads will be prevented fromentering the receiver.

In Fig. l the receiver R is provided with an input coil grounded at G asshown. Certain receivers, however, are equipped with input circuitscontaining floating coil or non-grounded primaries. For such receivers aset coupler like that illustrated in Fig. 2 is more appropriate andhence may be substituted in the circuit of Fig. l for that comprisingtransformers T3, T4.

In the circuit of Fig. 2 the down leads L1, Ia are extended throughcondensers C5, C6 respectively, to the input coil of receiver R. Thecapacities of condensers C5, C6 are such that they function as shortwave by-pass condensers but as long wave blocking condensers. A step-uptransformer T5 designed for efficient long wave reception, has itsprimary winding connected between conductors L1, L: on the. antenna sideof condensers C5, C6, and a secondary winding S5 connected between theseconductors or the receiver side of the condensers. The midtap of theprimary is connected to ground at G.

For the reception of long waves the electromagnetic coupling provided bythe transformer T5 is predominately effective in relaying signals to thereceiver due to the blocking action of condensers C5, Cs at these wavelengths. short wave lengths on the other hand the signals are by-passedin greater part past the transformer through condensers C5, C6, thetransformer windings then acting substantially as choke coils bridgedacross the line.

As regards elimination from the receiver of interfering currents inducedin the down leads L1, L2, the circuit of Fig. 2 functions in substancelike that of Fig. 1. Interfering currents i1, is directed in the samesense in conductors L1, L2, flow in opposite directions to ground at Gthrough the halves of the transformer primary P5, so that the fluxesproduced therein substantially annul one another.

The circuit of Fig. 3 is similar to the set coupler T3, T4 of Fig. 1except for the insertion in the connection I extending from themidpoints of the transformer primaries to ground at G, of a loadingimpedance H. Impedance H serves to increase the range of eflicientsignal reception in the long wave direction. Thus at long wave lengthsthe antenna and associated down lead circuit will operate as ahorizontal T antenna connected to ground through the loading impedanceH. Impedance H comprises a parallel resonant circuit which introduces ahigh impedance for frequencies in the neighborhood of .15 megacycles, inthe connection I extending from the midtaps of the transformer primariesP3, P4 1 to ground at G. At appreciably higher frequencies, however, thecondenser of impedance H functions as a by-pass condenser effectivelygrounding the midtaps of the transformer primaries P3, P4; with theresult that, at such frequencies, the operation of the Fig. 3 circuit isthe same as that of Fig. 1.

Reverting to the system ot Fig. 1, interference may be introduced intothe receiver by exposure to a local source of interference of anextremely long ground lead G, or one having appreciable impedance. Thisresults from the fact that a portion of an interfering current thusinduced in the ground lead will flow upward to the midtaps of theprimaries P3, P4, thence in inductive opposition through the halves ofthe primary windings to the respective down leads Ll, La, thence upwardthrough the down'leads and in inductive opposition through the halves ofthe long wave antenna transformer secondary winding S2 to the midtapthereof, thence through the associated primary P2 in the midtapconnection M, thence in inductive opposition through the halves of theshort wave antenna transformer primary P1 to the respective arms A, A1of the antenna and finally back to earth through the antenna-to-groundcapacities.

No interference is introduced in the receiver by the flow of thesecurrents through windings P3, P4, S2, P1,.owing to the inductiveopposition of the current flow in the halves of these windings. However,it will be observed that the total interfering current flows'in the samedirection through the primary P2, and thus induces an interferingvoltage in the associated secondary S2, which is relayed back to thereceiver along with the signal.

, Fig. 4 shows a modification of the Fig. 1 circuit wherein interferencepicked up by the ground lead is eliminated from the receiver, byinterposing in the down leads L1, L2 between the antenna transformersT1, T2 and the set coupler transformers T3, T4, a set of what might betermed long and short wave isolation transformers T6, T1. Thesetransformers are designed to have extremely small inherent capacitiesbetween their primary and secondary windings P6, S6 and P7, S1, theratio of primary to secondary turns being preferably substantially unityfor each transformer T6, T1. Moreover, except for these extremely smalland unavoidable inherent capacities the primary circuits are coupled totheir associated secondaries only through their mutual inductances.Short wave by-pass condensers C7 are connected between the innerterminals of windings P1 and S1 respectively.

As a result any tendency of interfering voltage induced in the groundlead G to cause interfering currents to traverse the down leads L1, L2and the long wave antenna primary P2 in the mannerexplained, issubstantially prevented by the isolating action of transformers T6, T7.Such current flow as does ensue will be practically restricted to thesecondary side of these transformers where the interfering currentstraverse the halves of the transformer primaries P3, P4 in inductiveopposition and likewise produce opposing effects in the secondaries S6,S1 of the isolation transformers T6, T1, in consequence of which nointerfering effects are produced in the associated primaries P6, P7 orin the receiver R.

Instead of employing transformers T6, T7 having separate primary andsecondary windings, an arrangement such as that shown in Fig. 2

i comprising elements C5, C6, T5 may be employed as the isolationcircuit. As so employed, condensers C5 and Cs should be selected ofextremely sm 11 capacity, of the order of micro-microfar ds each.

I claim:

1. In a radio receiving system: an antenna of the dipole type, a noisereducing downlead circuit for coupling said antenna over a pair ofadjacent conductors \to a radio receiver, an tenna coupling means forcausing received signals producing variations in potential of saidantenna with respect to ground to be impressed on said downlead circuit,a connection from ground to said receiver, and means for minimizingapplication to said receiver of noise producing voltages introduced intosaid ground connection, said means including a signal relayingtransformer in said downlead circuit, said transformer having separateprimary and secondary windings, the capacity between which offers a highimpedance to passage of noise producing currents.

2. In a radio receiving system: an antenna of the dipole type, a noisereducing downlead circuit for coupling said antenna over a pair ofadjacent conductors to a radio receiver, antenna coupling means forcausing received signals producing variations in potential of saidantenna with respect'to ground to be impressed on said downlead circuit,a connection from ground to said receiver, and means for minimizingapplication to said receiver of noise producing voltages introduced intosaid ground connection, said means including a signal relayingtransformer in said downlead circuit, said transformer having separateprimary and secondary windings of substantially unity ratio, thecapacity between which offers a high impedance to passage of noiseproducing currents.

3. In a radio receiving system: an antenna of the dipole type, atwo-conductor noise reducing downlead circuit for coupling said antennato a radio receiver, a connection to ground from said receiver, meanscoupling said antenna to said downlead circuit for causing said downleadcircuit to function as a counterpoise to said antenna to impress on saiddownlead circuit, signals producing variations in the potential of theantenna with respect to ground, and means for minimizing application tosaid receiver of noise producing voltages introduced into said groundconnection, said means comprising a signal relaying transformer in saiddownlead circuit adjacent said receiver, said transformer havingseparate primary and secondary windings, the

capacity between which offers a high impedence to the passage of noiseproducing currents.

4. In a radio receiving system, an antenna of the dipole type, atwo-conductor noise reducing downlead circuit for coupling said antennato a. radio receiver, an impedance bridging said circuit thereat, amidtap connection from said impedance to ground, means coupling saidantenna to said downlead circuit for impressing thereon signalsproducing variations in the potential of said antenna with respect toground, and means for minimizing application to said receiver of noiseproducing voltages introduced into said ground connection, said meanscomprising a signal relaying transformer in said downlead circuitbetween said} grounded impedance and said antenna, said transformerhaving separate primary and secondary windings, the capacity betweenwhich offers a high impedance to passage 'of noise producing currents.

5. In a radio receiving system for reception of long and short wavesignals, an antenna of the dipole type. a two-conductor downlead circuitfor coupling said antenna to a radio receiver, means for causingvariations in potential of said antenna with respect to ground due tolong wave signals to impress a signaling voltage on said downleadcircuit, means for impressing onsaid downlead circuit a signalingvoltage derived from potential differences occurring betweenelectrically spaced points of said antenna clue to short wave signals, acormection from ground to said receiver, long and short wave signalrelaying transformer means in said downlead circuit, said transformermeans having separate primary and secondary windings, the capacitiesbetween which oifer a high impedance to the passage of currents due tonoise producing voltages introduced into said ground connection.

6. In a radio receiving system for reception of long and short wavesignals: an antenna of the dipole type, a two-conductor downlead circuitfor coupling said antenna to.a radio receiver, an impedance bridgingsaid circuit thereat, a midtap connection from ground to said impedance,means for causing variations in potential of said antenna with respectto ground due to long wave signals to impress signaling voltages on saiddownlead circuit, means for impressing on said downlead circuitsignaling voltages derived from potential differences occurring betweenelectrically spaced points of said antenna due to short wave signals,long and short wave signal relaying transformer means in said downleadcircuit, said transformer means having separate primary and secondarywindings, the capacities between which offer a high impedance to thepassage of currents due to noise producing voltages introduced into saidground connection.

7. In a radio receiving system for reception of long and short wavesignals: an antenna of the dipole type having at least a pair of arms, atwo-conductor downlead circuit for coupling said antenna to a radioreceiver, means coupling said antenna to said downlead circuit forcausing signaling voltages occurring between the arms of said antennadue to short wave signals to be impressed on said circuit, meanscoupling said antenna to said downlead circuit for causing said circuitto function as a counterpoise for said antenna in impressing on saiddownlead circuit long wave signals producing variations in the potentialof said antenna with respect to ground, a connection from ground to saidreceiver, and long and short wave signal relaying transformer means insaid downlead circuit, said transformer means having separate primaryand secondary windings, the capacities between which offer a highimpedance to passage of noise producing voltages introduced into saidground connection.

8. In a radio receiving system in, combination: an antenna of the dipoletype, a two-conductor noise reducing downlead circuit for coupling saidantenna to a radio receiver, a connection from ground to said receiver,an antenna transformer having a secondary winding included in saiddownlead circuit and a primary winding in a connection extending fromsaid antenna to an intermediate point of said primary winding, and meansfor minimizing application to said receiver of noise producing voltagesintroduced into said ground connection, said means including a signalrelaying transformer in said downlead circuit, said transformer havingseparate conductively isolated primary and secondary windings, thecapacity between which offers a high impedance to passage of noiseproducing currents due to said ground connection.

JULIUS GOURGUES ACEV'ES.

